Continuous charging circuit for stabilized timers



1959 .H. E. RUEHLEMANN ETIAL 2,910,001

CONTINUOUS CHARGING CIRCUIT FOR STABILIZED TIMERS Filed May 27, 1952 Wmm1. Tu W EM Z, .O VE N n m E A H MW EM .R

United States Paten CONTINUOUS CHARGING CIRCUIT FOR STABILIZED TllYlERSHerbert E. Ruehlemann and Wolfgan A. Menzel, Silver Spring, Md.,assignors to the United States of America as represented by theSecretary of the Navy The invention described herein may be manufacturedand used by or for the Government of the United States of Americafor'governmental purposes without the payment of any royalties thereonor therefor.

This invention relates to electric fuze circuits and more particularlyto voltage stabilized time fuze circuits for use in bomb and rocketfuzes.

It is well known to use electrically energized fuzes in ordnanceequipment to initiate the operation thereof. The components generallyemployed to energize and control the time of operation of such fuzemechanisms include condensers, resistors and condenser discharge controldevices such as diodes arranged in various networks.

The problem of suitably charging the condensers for proper operation ofthe fuze mechanism of the specific piece of ordnance equipment beforerelease varies with the equipment. Such charging may be accomplishedeither by means of a pulse charging circuit, as disclosed in thecopending application, Serial No. 219,302, filed April 4, 1951, whereinstabilization is completed before the timing cycle starts, or acontinuous charging circuit wherein the stabilization condenser iscontinuously being recharged through a long time constant circuit asdisclosed in the instant application. The instant invention representsan improvement over the stabilization circuits there shown anddisclosed.

Due to the electrical and mechanical variations in the diodes used inelectrically actuated fuzes, as in the instant case, a specialstabilization method is used in which the voltage on a condenser isadjusted to the exact value of the breakdown voltage of the diode usedin the particular piece of ordnance equipment. This stabilization methodis disclosed in the copending application previously referred to and formore complete information on this method reference thereto should bemade.

Cold cathode diodes used in such stabilization circuits are normallyconnected during the charging cycle or directly thereafter to thestabilization device including the stabilizing condenser and 'whenstabilization is accomplished, the diode is switched to the ignitioncircuit. Such switching action can be performed quite easily in a shellfuze where charging of the fuze circuit can be accomplished in thebreech of a gun and the diode switching is a function of the firing ofthe shell. However, in bombs and rockets equipped with voltagestabilized time fuze circuits where the charge on the condensers has tobe applied to the ignition circuit at the instant of dropping or firingthe missile, this switching cannot be as readily accomplished, sincewhen the bomb or rocket is in flight no forces are acting which can beused to perform such switching action. It would therefore be necessaryto provide an additional delay mechanism to operate the diode switching.In order to avoid the use of clockwork mechanisms or pyrotechnicdevices, which are undesirable and space consuming, it is proposed bymeans of the novel circuit arrangements herein disclosed to continuouslycharge the stabilizing condenser through a high resistance, shunted witha diode, additional to the conventional diode in the stabilizingcircuit, for a certain time prior to the release of the bomb or rocket.The arrangement of the high resistance shunted by the diode immediatelyplaces a momentary overvoltage on the stabilizing condenser without theinitial use of the diode in the stabilizing circuit. This arrangementpermits the stabilizing process to be started at the instant the masterpower supply switch is turned on and immediately places the stabilizingcircuit in operation and provides suflicient energy to the ignitioncircuit at the instant of release of the missile without having to firstperform a diode switching operation involving the use of delaymechanisms, in the fuze. The diode switching in a missile having'voltagestabilized time fuze circuits can then be performed by the mechanismsecuring the bomb or rocket to the aircraft at the instant of release.

In order to overcome the problems indicated above in performingswitching of the diode from the voltage stabilizing to the ignitioncircuit necessitated by the use of stabilized timer circuits in missilessuch as bombs and rockets, it is a primary object of this invention toprovide means other than mechanical or pyrotechnic devices to performsuch diode switching.

It is a further object of this invention to provide in a voltagestabilized circuit means for applying a quick charge to the stabilizingcondenser.

It is a further object of this invention to provide a voltage stabilizedtimer circuit wherein a continuous charge must be applied to thestabilizing condenser and may be applied to other condensers in the fuzecircuit.

It is a further object of this invention to provide in an electric fuzecircuit means whereby a slow charge may be applied to the voltagestabilizing condenser after an initial quick charge to initiate thevoltage stabilizing process.

It isa further object of this invention to provide in a voltagestabilized time fuze circuit means whereby said circuit providesadequate energy to the ignition circuit of a bomb or rocket type missileat the instant of release.

It is a further object of this invention to provide in a voltagestabilized time fuze circuit of a bomb or rocket type missile means forswitching a diode from the stabilizing circuit to the ignition circuitat the instant of release of the missile.

'It is a further object of this invention to provide in a voltagestabilized time fuze circuit means to reduce to a minimum the time forcharging the stabilizing condenser and initiating the first step of thestabilizing process.

It is a further object of this invention to provide a voltage stabilizedtime fuze circuit for electric fuzes using continuous charge wherein ahighrate of change of voltage setting may be applied to the fuzecircuit.

Other objects. and many of the attendant advantages of this inventionwill be readily appreciated as the same becomes better understood byreference to the following detailed description when considered inconnection with the accompanying drawings wherein:

On the drawing is shown one form of a voltage stabilized time fuzecircuit diagram embodying the principles of the instant invention.

Referring to the drawing there is shown to the left of line A--A, avoltage divider 5 which is connected across the power supply ofterminals 1, 2 and a switch S which may be the master power switch of anaircraft. To the right of the line A--A there is shown a continuouscharging arrangement for a voltage stabilized time fuze circuit. Uponrelease of the missile, the fuze circuit is disconnected from the powersupply at A-A. Switches 15 and 16 are actuated by the missile supportingdevice such as an aircraft bomb rack or rocket launching mechanism sothat upon release the switches 15 and 16 are closed and connect thecondensers 12, 22, 23 in series with the ignition circuit, includingdetonator 14. The switch S is an additional switch, installed on themissile, which may be used to disconnect the fuze circuit from the powersupply.

The continuous charge voltage stabilized. fuze circuit illustrated inthe form of the invention shown in the sole figure comprises the timingcondenser 12 shunted; by its discharge resistance 13-, which condenser,when switches, 15, 16- are actuated by the release mechanism, isconnected in series with diode 19 and with stabilizing condenser 22 andcondenser 23. In conventional ignition circuits, the function performedby condensers 22 and 23 in the instant invention are generally performedby a single condenser. In the instant invention condenser 23 provides areference voltage for setting the cycling rate of the voltagestabilization circuit; while the voltage on the stabilizing condenser22- is exactly equal to the breakdown voltage of the diode 19. Thecharging circuit forthe stabilizing condenser 22 includes a high megohmresistor 18 shunted by a diode 17 The proper operation of the circuitrequires a high value of resistance connected in series with stabilizingcondenser 22 therebyrequiring a long time to charge this condenser tothe'breakdown voltage of 'the diode 19; The diode 17 is thereforeprovided to short the resistance 18 when the master switch S1 is-closedto momentarily apply an overvoltage to the stabilizing condenser 22thereby to start the stabilizing process which continues until releaseof the missile. At the instant of release with condensers 12 and 23charged, the diode 19 is switched from the stabilizing circuit to theignition circuit by the operation of switches 15 and 16 as a consequenceof the release of the missile.

Due to the initial charge on condenser 12,. insufficient potentialexists across diode 19 to render diode 19 conductive for dischargingcondenser 22 through detonator 14. After a predetermined time interval,as determined by the discharge rate of condenser 12 through resistor 13,the potential difference across diode 19 will become suflicient torender diode 19 conductive whereupon the charge on condenser 22 will bedischarged through the diode and ignite the detonator.

In addition to the advantages previously indicated, by the use ofcontinuous charging circuits for voltage stabilized time fuzes there isthe additional advantage that the rate of change of voltage acrosscondenser 12 can be higher since the rate of change influenced only bythe time constant of the reference voltage condenser 23. ince thi n ensr is n rmally of. a small value, the resistance of the voltage dividerhas little influence on the charging time of the timing condenser, anConsequently upon the rate of change of voltage across condenser 12,which in turn has a, direct efiect on, the fuze time setting.

To obtain continuous charging of condenser 22. and stabilization stepsat a frequency which will not influence the stabilizing and voltagebreakdown of diode 19, a high value of resistance 18 is connected inseriesiwith, condenser 22. If such a large resistance were placed in.the. power supply, the value of insulation resistance, of the fuzecircuit would have to be considerably higher to obtain the properpotential on condenser 22,. Proper, balance of circuit components wouldbe diflicult under such conditions especially to meet military servicerequirements. It is therefore, necessary to include resistance 18 in thefuze directly. connected to the condenser 22. Additionally, in thisposition resistance 18 cannot be shortcdduring the charging cycle by thepower supply to obtain a momentary overvoltage on condenser 22 toinitiate the stabilizing process because switching action takes placein; the power supply and not in the fuze. However with. resistance 18connected in series with condenser 22 the time required to chargecondenser 22 high enough to start the stabilizing process is. severalminutes which is too long for military purposes. To overcome thisdifficulty, a cold cathode diode 17 is connected in parallel withresistor 18.

At the instant of closing the master power switch S in the power supply,condenser 22 is charged through the diode 17 to a value equal to theapplied voltage minus the extinguishing potential of the diode 17. It istherefore possible to provide a momentary voltage on condenser 22 whichis higher than the breakdown voltage of h odc19 t us momen ari ystarting a p lse. stabil tion action whichcontinues until theovervoltage on condenser 22 is drained down to the stabilization voltageas determinedv by the extinguishing potential of diode 19.. At thisinstant the pulse stabilization action is followed automaticallybyacontinuous stabilization process deter- "mined only; by theovervoltage and the resistance value of resistor 18.

The operation of the stabilizing process using continuous charging willnow be described. Before charging the fuze or releasing the missile themaster power switch S is moved to a position such that terminals 6a, 7aand 8a are in the circuit and in this position the three condensers 12,22 and" 23' are shorted to ground and so discharged. For operation, theswitch S1 is'moved from the short position to the chargeposition therebyplacing contacts 6, 7' and 8 in circuit. At the instant of switching tothe charge position the three condensers 1'2, 22- and 23 are connectedto the voltage divider 5 of the power source. Condensers 12 and 23 arecharged directly from the source but condenser 22 is indirectlyconnected. to the power-source by way of the diode 1'7 which breaks downat the instant of closing the master switch S1 thereby chargingcondenser 22 to a voltage equal to the potential in the power supplyminus the potential drop across diode 1'7; Diode 17' then stopsconducting thereby interrupting the initial charging path to condenser22. At this, instant the condenser 22 ignites the diode I9d'ischargingrnt h c ndens r 21 un il. the voltag in condenser 21 is high enough toreduce the potential across diode 19 below the sustaining level off thediode 19' wh re p n h is harge. of cond nser. 22. is interrupted. Thecondens r .21 then partially'loses. its energy hro gh the resistor 20and when, the voltage, in condenser 21 is lowered, enough the diode. 19again ignites. This is. the so-called stabilization process as used in,the stabilization circuits disclosed in the copending applicationpreviously mentioned. By this stabilization operatio e volta acrosscondenser will be lowered to-a valueiust below the. bre k own age ofdiode 19 so thatfurthcr abi: lization t p are. not. p ssi le- In hircnithercin discl sed. the cond nser 22 is c n in o sly connected tothe power upply bet re release of the. missile thro gh a high resistanceelement 18 which is in parallel with. diode 17. The condenser 22 isthereby continuously recharged through the resistor 18 at, a; very hightime constant, After about 2,1 S6Q0fid101? more the voltage in condenser22. is again increased to the breakdown voltage of diode. 19 whereupondiode 19commences to conduct and, partially discharges condenser 22 anda. new stabilization step. occurs. This cycling operation is repeatedduring the entire time the fuze isconnected to the power- Supply untilthe instant themissile is released and the stabilizing circuit disconneted. fr m. he power supply. I

Qbviously many modifications and variations of the present invention arepossible in the. light of the. above teachings. It is therefore to beunderstood that within th scope of the pp nded laims he. invention. maybe. practiced. otherwise than as specifically described.-v

What is claimed. and desired to be secure by. Letters Patent of theUnited States is:

1. A charging circuit comprising a. voltage stabilizing device, a timingmeans connected to said device, means connected to said stabilizingdevice for developing a voltage pulse to initiate operation of saidstabilizing device atthe instant of energization ofsaidstabilizingdevice and thereafter for developing aconti'nuous charge to said device,reference voltage means connected to said device, means for energizingsaid stabilizing device and said reference means, and means fordisconnecting said energized stabilizing device from said energizingmeans.

' 2. A voltage stabilizing fuze circuit for a missile comprising a firstRC timing circuit, a second RC circuit, a first condenser formaintaining a reference potential serially conected to a secondcondenser capable of being charged to a voltage in excess of saidreference voltage, said second condenser serially connected to saidsecond RC circuit through a first electron discharge device, animpedance network including a long time constant resistance and a secondelectron discharge device connected in parallel with said resistance,said impedance network being serially connected to said second condenserfor applying a pulse voltage thereto for initiating a stabilizingprocess, said resistance thereafter applying a long time constant chargeto said second condenser, an ignition circuit including anelectro-responsive igniter, means for instantly connecting saidstabilizing circuit to said ignition circuit through said first RCcircuit. and said first electron discharge device, energizing means forsaid fuze circuit, and means for connecting and disconnecting saidenergizing means from said fuze circuit.

3. A voltage stabilizing circuit comprising an energizing source, anenergy storage device chargeable. by said source, a discharge circuitconnected across said energy storage device for successively dischargingthe charge on said energy storage device to a predetermined chargelevel, and circuit means interposed between said energizing source andsaid energystorage device for developing an initial energizing impulsefor said energy storage device and for thereafter developing acontinuous energizing charge for said energy storage device from saidsource.

.4. A voltage stabilizing circuitcomprising an energizing source, afirst energy storage device connected to said energizing source adaptedto be charged to a predetermined energy level therefrom, a second energystorage device chargeable by said energizing source, circuit meansincluding a parallel coupled gas discharge device and impedance elementinterconnecting said source to said second storage device for applyingan initial energizing impulse and for thereafter applying a continuousenergizing charge to said second storage device, and a discharge circuitconnected across said second storage device for successively dischargingsaid second storage device to a predetermined energy level at a ratecorrelative to the charge on said first storage device.

5. A voltage stabilizing circuit comprising an energizing source, anenergy storage device chargeable by said source, a discharge circuitconnected. across said energy storage device for successivelydischarging the charge thereon to a predetermined charge level, saiddischarge circuit including a serially connected parallel R-C networkand gas discharge device adapted to be successively rendered conductiveand nonconductive, and circuit means interposed between said source andsaid storage device for providing an initial energizing impulse to saidstorage device and for thereafter providing a continuous energizingcharge to said storage device from said source.

6. A voltage stabilizing circuit comprising an energization source, anenergy storage device chargeable by said source, a discharge circuitconnected across said energy storage device forsuccessively dischargingthe charge on said energy storage device to a predetermined chargelevel, and a parallel coupled resistance and gas discharge deviceinterposed between said energizing source and said energy storage devicefor providing an initial energizing impulse to said energy storagedevice and for thereafter providing a continuous energizing charge tosaid energy storage device from said source. g

7. A time fuze circuit comprising an electroresponsive detonator, afirst'energy storage device connected to said detonator being chargeableto a predetermined energy level and dischargeable to a predeterminedlevel at a predetermined discharge rate, a second energy storage devicechargeable to a predetermind energy level, a third energy storage deviceconnected to said second storage device and chargeable to apredetermined energy level, an energizing source, circuit means forconnecting said first, second and third energy storage devices to saidsource, said circuit being adapted to apply an initial energy impulseand thereafter a continuous energy charge to said second storage device,a discharge circuitconnected across said second storage device fordischarging said second storage device to a predetermined energy level,and switching means for discretely connecting said second storage deviceto said first energy storage device through said discharge circuit fordischarging said second storage device through the detonator at a timecorrelative to the discharge rate of said first storage device.

References Cited in the file of this patent UNITED STATES PATENTSGuanella Aug. 21, 1956

